A workpiece stack-up that includes at least a steel workpiece and an aluminum-based workpiece can be resistance spot welded by employing a multi-stage spot welding method in which the passage of electrical current is controlled to perform multiple stages of weld joint development. The multiple stages include: (1) a molten weld pool growth stage in which a molten weld pool is initiated and grown within the aluminum-based workpiece; (2) a molten weld pool solidification stage in which the molten weld pool is allowed to cool and solidify into a weld nugget that forms all or part of a weld joint; (3) a weld nugget re-melting stage in which at least a portion of the weld nugget is re-melted; and (4) a re-melted weld nugget solidification stage in which the re-melted portion of the weld nugget is allowed to cool and solidify.

A method of resistance spot welding a steel workpiece and an aluminum or aluminum alloy workpiece together includes several steps. In one step a workpiece stack-up is provided. The workpiece stack-up includes a steel workpiece and an aluminum or aluminum alloy workpiece. Another step involves providing a first welding electrode that confronts the aluminum workpiece, and providing a second welding electrode that confronts the steel workpiece. The first welding electrode has an electrode body and an insert that functions to limit or eliminate heat flux into the electrode body. Other steps of the method involve bringing the first and second welding electrodes into contact with opposite sides of the workpiece stack-up and resistance spot welding the stack-up.

Resistance spot welding of a steel workpiece to an aluminum or an aluminum alloy workpiece can be facilitated by replacing the refractory aluminum oxide-based layer(s) on at least the faying surface of the aluminum or aluminum alloy workpiece with a protective coating that is more conducive to the spot welding process. The protective coating may be a metallic coating or a metal oxide conversion coating. In a preferred embodiment, the protective coating is a coating of zinc, tin, or an oxide of titanium, zirconium, chromium, or silicon.

The base member 3 can be attached to and detached from a base-holding member 5 without using tools and the like. The base-holding member 5 has a positioning mechanism that decides the position of the base member 3 on the base-holding member 5. Here, a reference part that decides the position of the base member 3 on the base-holding member 5 in a direction parallel to an optical fiber installation surface 2, which is an upper surface of the base member 3, is called a horizontal positioning reference part. Also, a reference part that decides the position of the base member 3 on the base-holding member in a direction vertical to the optical fiber installation surface 2 (the direction vertical to the horizontal positioning reference part), which is the upper surface of the base member 3, is called a vertical positioning reference part 6. That is, the horizontal positioning reference part and the vertical positioning reference part 6 are provided on the base-holding member 5.

The base member 3 can be attached to and detached from a base-holding member 5 without using tools and the like. The base-holding member 5 has a positioning mechanism that decides the position of the base member 3 on the base-holding member 5. Here, a reference part that decides the position of the base member 3 on the base-holding member 5 in a direction parallel to an optical fiber installation surface 2, which is an upper surface of the base member 3, is called a horizontal positioning reference part. Also, a reference part that decides the position of the base member 3 on the base-holding member in a direction vertical to the optical fiber installation surface 2 (the direction vertical to the horizontal positioning reference part), which is the upper surface of the base member 3, is called a vertical positioning reference part 6. That is, the horizontal positioning reference part and the vertical positioning reference part 6 are provided on the base-holding member 5.

A tab guide according to an embodiment of the present invention may press a plurality of electrode tabs so that the plurality of electrode tabs are gathered together.

The tab guide may include a contact part, which is in contact with the electrode tabs, and a mounting part in which the contact part is detachably mounted and which has higher rigidity than that of the contact part.

A tab guide according to an embodiment of the present invention may press a plurality of electrode tabs so that the plurality of electrode tabs are gathered together.

The tab guide may include a contact part, which is in contact with the electrode tabs, and a mounting part in which the contact part is detachably mounted and which has higher rigidity than that of the contact part.

A second joining flange formed along an edge of a second panel and a third joining flange formed along an edge of a third panel are superimposed on a first joining flange formed along an edge of a first panel, a seam weld is made in a section in which the first joining flange and the second joining flange form two layers and a section in which the first joining flange and the third joining flange form two layers, and a spot weld is made in a section in which the first joining flange, the second joining flange and the third joining flange form three layers. Such structure enhances production efficiency by increasing welding speed, and facilitates spot welding in the section having three layers, for which seam welding is difficult due to the large number of superimposed sheets, thereby enhancing strength against peel-off.

A welding cap cooling water control system has a cooling water conduit with a cooling water inflow leading in direction of the welding cap and a cooling water return flow leading away from the welding cap, in which a flow sensor and a control valve are seated. On the side of the inflow or the return flow the cooling water flow is controlled by a flow control valve which also serves for emergency shut-off in the case of pressure loss.

A method for welding metal components to weld a first metal piece and a second metal piece to form a metal component comprises the steps of: positioning a first working portion of the first metal piece against a second working portion of the second metal piece to jointly form an intended welding seam; performing local welding on the intended welding seam to form a plurality of welding zones and a plurality of non-welding zones that are spaced from each other; providing a bonding paste to fill the non-welding zones and providing a curing condition to cure the bonding paste to mask the non-welding zones to finish welding of the first metal piece and the second metal piece to form the metal component.